Could you please tell me the meaning of "took the heart out of" in the following excerpt from The Great Gatsby, Chapter Five?
A brewer had built it early in the “period” craze, a decade...

Could you please tell me the meaning of "took the heart out of" in the following excerpt from The Great Gatsby, Chapter Five?

A brewer had built it early in the “period” craze, a decade before, and there was a story that he’d agreed to pay five years’ taxes on all the neighboring cottages if the owners would have their roofs thatched with straw. Perhaps their refusal took the heart out of his plan to Found a Family—he went into an immediate decline.

The meaning of the phrase "took the heart out of" refers to the idea that the "animating spirit" or the "main force" of the man's idea has been lost.

The man who built the mansion and the surrounding cottages being discussed here had big plans to shape the character of his neighborhood. He intended to act on the "period craze" which was a short-lived interest in designing, building and decorating homes inspired by different historical periods. This man's idea was to create a feudal or pastoral neighborhood with his own house as the castle over-looking it all.

When the neighbors refuse to go along with the idea and put thatched roofs on their houses, the man's idea loses its momentum and/or the man loses his interest in carrying out his plan. The energy that had animated his proposals has been lost; the heart of the plan was lost.

The man goes into decline and dies. Nick comments that the plan did not work because:

"Americans, while occasionally willing to be serfs, have always been obstinate about being peasantry."

The implication is that the brewer had hopes of elevating himself above his neighbors to become their symbolic king or superior.

(Often times, the phrase "heart of" is used to suggest the core or center of something. In this case, the phrase carries connotations of that center being defined or aligned with emotional energy, motivation, etc.)